1. Technical field of the Invention
The present invention relates to an electronic control apparatus for vehicles, and in particular, to the electronic control apparatus which is provided with a sensor to detect a submerged state of a vehicle and which has the capability of performing control to secure the safety of the occupants when the vehicle is about to be submerged.
2. Related Art
When a vehicle runs through a flooded road which is flooded due to river water, rain, or sea water, there is a risk that an electronic control apparatus to control the behaviors of the vehicle may malfunction. In order to avoid such a condition, a conventional electronic control apparatus has been known, which performs various kinds of control for securing the safety of the occupants when the vehicle is about to be submerged or partly submerged This kind of apparatus, which is installed within the vehicle, is provided with a sensor to detect a submerged state of a vehicle and a control IC that uses a signal detected by the sensor. This sensor, called a submersion sensor, has a pair of mutually opposed electrodes which are placed in parallel with a space therebetween.
In this kind of electronic control apparatus, when the vehicle is about to be submerged in a flooded region, the submersion sensor will detect a vehicle's submerged state by allowing leak current to flow between the mutually opposed electrodes (i.e., sensor electrodes) submerged in the water. When this submergence is detected, the control IC controls actions to prevent the vehicle, which actions include an action to cut off current from the battery to the starter for starting the engine so that the starter is prevented from malfunctioning due to the submergence.
Another known conventional electronic control unit with countermeasures for the submergence is provided with a single circuit board which is parallel to a plane horizontally installed within a vehicle (i.e., vehicle horizontal plane). A submersion sensor, a control IC and other necessary components are mounted on this vehicle horizontal plane.
Concerning this electronic control apparatus with such a circuit board, it is desired that the control IC be prevented from malfunctioning before the submersion sensor first detects the vehicle's submerged state. For this prevention, Japanese Patent Laid-open Publication No. 2006-317298 discloses a unit structure where an enclosure encloses necessary circuit components including the control IC so that the submersion sensor and the necessary circuitry other than the sensor electrodes are prevented from being wet.
However, in this electronic control apparatus with the circuit board in parallel with the vehicle horizontal plane, it is necessary that a plurality of submersion sensors must be installed on the circuit board to detect vehicle tilts and submergence in every way. This installation manner results in an increase in the number of parts for the apparatus, thereby increasing manufacturing costs of the apparatus.
In addition, in this electronic control apparatus, the necessary components including the submersion sensors and the control IC are mounted on the same circuit board. Hence, if it is desired in this apparatus that a blank space of the circuit board, which has no wiring, is reduced as much as possible to make the board area smaller but the sensor electrodes are kept to be exposed, it is necessary to give a complicated shape to the enclosure. This results in a problem that the structure of the apparatus becomes complex.
That is, the electric control apparatus exemplified by the foregoing publication often increases the number of parts and makes the apparatus structure complex, which may cause in an increase in manufacturing costs of the apparatus.